The present invention relates to the art of geotextile containers of the type for maintaining fill material.
Geotextile containers adapted to serve as receptacles for soil, aggregate or other fill material are utilized in a variety of applications. For example, elongated geotextile containers such as the bags that are disclosed in U.S. Pat. No. 3,957,098 are often utilized in a body of water, such as a bay or a river, to facilitate control of erosion. Such bags are formed of two layers of rectangular fabric overlying each other. Each long edge of each layer is double-stitched with lock stitches to the opposed long edge of the other layer. In a typical application, an elongated container of this type may be situated to extend generally in parallel, perpendicular or at various angles with respect to the shoreline. Such a container may be filled with material dredged from the bottom of the body of water to provide weight to maintain the container in position. The area between the container and the shoreline may be backfilled with soil to effectively extend the shoreline farther out into the body of water. Containers of this type may also be used as a receptacle for contaminated material.
An elongated geotextile container may have a length of up to about 2,000 feet or more. The circumference will generally depend on the desired barrier height, but a circumference of about forty-five (45) feet or more is also not unusual. When the container is filled, it can be under water and can include an inner liner and an outer shell. The hydrostatic pressure on the outside of a submerged container, must be overcome by the dredging pumps that are used to fill the container in order to displace the water atop and inside the container. Thus, the pressure applied by these pumps, as well as the weight of the fill inserted into the container, will result in outwardly directed forces that stress the geotextile fabric and the seams that join the sheets of the fabric composing the container. The rupture strength of the geotextile material composing each sheet in the container structure, can be on the order of 1000 pounds of force, depending on a number of factors. These factors include the polymer composition of the fabric, the weave, and the denier of the fibers in the fabric.
However, the rupture strength of each of the seams that connects adjacent sheets of geotextile material composing the container, is believed to be on the order of 50% of the strength of the geotextile fabric composing the sheet and depends upon the type of seam, the polymer composing the fabric, the polymer composing the sewing thread, the denier of the sewing thread, and the type of stitch made with the sewing thread. Accordingly, the seams are the weakest link in the construction of the container. The strength of the seams determines the maximum force to which the container can be subjected, before the container will burst and thus fail.
The problems posed by the relatively weak sewn seams in each end of an elongated geotextile container, have been addressed in one container of the type disclosed in commonly assigned U.S. Pat. No. 5,505,557, which is hereby incorporated herein by this reference. A bag defining an inner cavity permits the fill material to be contained therein. The bag is constructed of at least two elongated rectangular sheets of a flexible material opposed to one another and sewn along the opposed long edges to form at least two axial seams and sewn along the opposed short edges to form at least one end seam at a closed end. The closed end is back-folded into the inner cavity to form a pouch. An outer surface of the bag thus defines an inner surface of the pouch. Likewise, an inner surface of the bag defines an outer surface of the pouch. At least one anchor object is positioned in the pouch and tied off by a clamping mechanism situated about a neck portion of the pouch. As a result, the pouch is closed and the anchor object is maintained on the inside thereof. Due to this construction, an axially outward force imparted by the fill material will be directed against the inner surface of the bag instead of directly against the end seam in the closed end. However, this solution does not address the adverse effect of the radially directed forces upon the longitudinal seams of the container.
Moreover, because of the large circumferences of some geotextile containers, if a single wide sheet is desired to span the circumference of the container, a very large (and expensive) loom is needed to weave the sheet of such width. Alternatively, a number of smaller width sheets must be seamed together along their lengths to form a single large diameter container. In another alternative, a number of smaller diameter containers must be bundled together to attain the desired overall diameter required by the application. However, each of these latter alternatives results in a number of longitudinal seams, which are less desirable as noted above. Moreover, even a container formed of a single sheet of massive width, nonetheless has at least one longitudinal seam that is believed to reduce the strength of the overall container by 50% of the strength of the fabric forming such sheet of geotextile material.
Still another alternative relies on a circular loom to produce a fabric in a continuous tubular shape without any longitudinal seam. However, this alternative also has its limitations. The tubular fabric woven by such circular looms does not have the large circumference that is desired. Such circular looms are themselves more expensive than a conventional loom. Such circular looms cannot weave some types of synthetic yarns that are desirable for forming the heavier and stronger fabrics, which are desirable for their strength and for the larger circumference applications. This is due to the inability of a circular loom to weave a fabric composed of yarns that are relatively thick and/or stiff.